1. Field of the Invention
This invention relates to vapor storage canisters for vehicle fuel vapor loss control systems in general, and specifically to a canister assembly kit including a canister body and a series of modular fuel trap subassemblies that allow the canister body to be installed in multiple possible orientations.
2. Description of the Related Art
Vehicle fuel vapor loss control systems typically include a vapor storage canister assembly. The canister includes a hollow body that contains a bed of fuel vapor adsorbent, usually activated carbon, and various openings to receive vapors from the fuel system, to purge out stored vapors, and to admit fresh air. Fuel vapors may be received just from the fuel tank, or, in proposed systems, from a tank vent vapor valve also, so as to control fuel fill losses.
With the prospect of increased demands on the capacity of the canister, the problems of increased canister volume and under hood packaging constraints have become a concern. Furthermore, with greater fuel vapor handling demands on the canister come more possibilities for the introduction of liquid fuel into the canister, either directly or from fuel vapor condensation. Liquid fuel can contaminate or degrade the efficiency of the adsorbent. Designs for canisters with trap chambers to keep the liquid fuel away from the adsorbent may be seen in U.S. Pat. No. 4,714,485, assigned to the assignee of the current invention. In one embodiment, an upright cylindrical canister has its adsorbent bed spaced away from the bottom of the canister, creating an internal chamber. Both the vapor inlet tube and purge tube open into the chamber, where liquid may collect and be withdrawn, isolated from the lower surface of the adsorbent bed. In another embodiment, a reclining can is first filled with a bed of adsorbent confined between a pair of filter screens. The screens are not capable of physically retaining the adsorbent, so the ends of the canister must have separate closures. One end of the canister is closed by a cap with a fresh air inlet. The opposite end of the canister is closed by two components, first a partition that opens to the adsorbent bed, and then a dish shaped cover that goes over the partition and forms a chamber. A vapor inlet and purge tube both open through the end of the cover into the chamber, with an inlet of the purge tube located near the bottom of the chamber so as to draw out trapped liquid during purge. Both the cap and cover must be glued or welded securely to the ends of the canister.
Each of the embodiments in the patent above are capable of only a single installation orientation. That is, the upright canister cannot be mounted in a reclining orientation, nor can the reclining canister be installed upright. Moreover, once the cover is attached, the reclining canister cannot be turned 90 degrees, because the purge tube would then be dislocated. In addition to requiring separate assembly steps, the use of a cover separate from the canister makes it impractical to make the cover from a material different from the canister itself, if sonic welding is to be used to attach it. Since the trap will hold liquid fuel, while the body of the canister itself will not, it may be desirable to use dissimilar materials for the two parts.